Download Chapter 1: Introduction

Chapter 1: Introduction
Operating System Concepts – 9th Edit9on
Silberschatz, Galvin and Gagne © 2013
Chapter 1: Introduction
1. What Operating Systems Do
2. Computer-System Organization
3. Computer-System Architecture
4. Operating-System Structure
5. Operating-System Operations
6. Process Management
7. Memory Management
8. Storage Management
9. Protection and Security
10. Kernel Data Structures
11. Computing Environments
12. Open-Source Operating Systems
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1.9 PROTECTION AND
SECURITY
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Protection and Security
 Protection – any mechanism for controlling access of processes or
users to resources defined by the OS
 Security – defense of the system against internal and external attacks

Huge range, including denial-of-service, worms, viruses, identity
theft, theft of service
 Systems generally first distinguish among users, to determine who can
do what
 User identities (user IDs, security IDs) include name and
associated number, one per user
 User ID then associated with all files, processes of that user to
determine access control

Group identifier (group ID) allows set of users to be defined and
controls managed, then also associated with each process, file
 Privilege escalation allows user to change to effective ID with
more rights
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1.10 KERNEL DATA
STRUCTURES
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1.10.1 Lists, Stacks, and Queues
 Many similar to standard programming data structures
 Singly linked list
 Doubly linked list
 Circular linked list
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1.10.2 Trees
 Binary search tree
left <= right

Search performance is O(n)

Balanced binary search tree is O(lg n)
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1.10.3 Hash Functions and Maps
 O(1)
 hash collision
 Hash function can create a hash map

associates (or maps) [key:value] pairs using a hash function
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1.10.4 Bitmaps
 Bitmap – string of n binary digits representing the status of n items

the availability of each resource is indicated by the value of a
binary digit: 0 means that the resource is available, while 1
indicates that it is unavailable (or vice-versa)

001011101
 Linux data structures defined in
include files <linux/list.h>, <linux/kfifo.h>,
<linux/rbtree.h>
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1.11 COMPUTING
ENVIRONMENTS
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1.11.1 Traditional Computing
 Stand-alone general purpose machines
 But blurred as most systems interconnect with others (i.e., the Internet)
 Portals provide web access to internal systems
 Network computers (thin clients) are like Web terminals
 Mobile computers interconnect via wireless networks
 Networking becoming ubiquitous – even home systems use firewalls
to protect home computers from Internet attacks
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1.11.2 Mobile Computing
 Handheld smartphones, tablets, etc
 What is the functional difference between them and a “traditional”
laptop?

Extra feature – more OS features (GPS, gyroscope)

Allows new types of apps like augmented reality

Use IEEE 802.11 wireless, or cellular data networks for
connectivity
 Leaders are Apple iOS and Google Android
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1.11.3 Distributed Systems
 Distributed computing

Collection of separate, possibly heterogeneous, systems
networked together


Network is a communications path, TCP/IP most common
–
Local Area Network (LAN)
–
Wide Area Network (WAN)
–
Metropolitan Area Network (MAN)
–
Personal Area Network (PAN)
Network Operating System provides features between systems
across network

Communication scheme allows systems to exchange
messages

Illusion of a single system
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1.11.4 Client–Server Computing
 Client-Server Computing

Dumb terminals supplanted by smart PCs
 Many systems now servers, responding to requests generated by
clients
 Compute-server system provides an interface to client to
request services (i.e., database)

File-server system provides interface for clients to store and
retrieve files
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1.11.5 Peer-to-Peer Computing
 Another model of distributed system
 P2P does not distinguish clients and servers

Instead all nodes are considered peers

May each act as client, server or both

Node must join P2P network


Registers its service with central lookup service on network, or

Broadcast request for service and respond to requests for
service via discovery protocol
Examples include Napster and Gnutella, Voice over IP (VoIP)
such as Skype
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1.11.6 Virtualization (1)
 Allows operating systems to run applications within other OSes

Vast and growing industry
 Emulation used when source CPU type different from target type (i.e.
PowerPC to Intel x86)

Generally slowest method

When computer language not compiled to native code –
Interpretation
 Virtualization – OS natively compiled for CPU, running guest OSes
also natively compiled

Consider VMware running WinXP guests, each running
applications, all on native WinXP host OS

VMM (virtual machine Manager) provides virtualization services
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1.11.6 Virtualization (2)
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1.11.6 Virtualization (3)
 Use cases involve laptops and desktops running multiple OSes for
exploration or compatibility

Apple laptop running Mac OS X host, Windows as a guest

Developing apps for multiple OSes without having multiple systems

QA testing applications without having multiple systems

Executing and managing compute environments within data
centers
 VMM can run natively, in which case they are also the host

There is no general purpose host then (VMware ESX and Citrix
XenServer)
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1.11.7 Cloud Computing (1)

Delivers computing, storage, even apps as a service across a network

Logical extension of virtualization because it uses virtualization as the base for it
functionality.


Amazon EC2 has thousands of servers, millions of virtual machines,
petabytes of storage available across the Internet, pay based on usage
Many types

Public cloud – available via Internet to anyone willing to pay

Private cloud – run by a company for the company’s own use

Hybrid cloud – includes both public and private cloud components

Software as a Service (SaaS) – one or more applications available via the
Internet (i.e., word processor)

Platform as a Service (PaaS) – software stack ready for application use via
the Internet (i.e., a database server)

Infrastructure as a Service (IaaS) – servers or storage available over
Internet (i.e., storage available for backup use)
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1.11.7 Cloud Computing (2)
 Cloud computing environments composed of traditional OSes, plus
VMMs, plus cloud management tools

Internet connectivity requires security like firewalls

Load balancers spread traffic across multiple applications
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1.11.8 Real-Time Embedded Systems
 Real-time embedded systems most prevalent form of computers

Vary considerable, special purpose, limited purpose OS, real-time
OS

Use expanding
 Many other special computing environments as well

Some have OSes, some perform tasks without an OS
 Real-time OS has well-defined fixed time constraints

Processing must be done within constraint

Correct operation only if constraints met
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1.12 OPEN-SOURCE
OPERATING SYSTEMS
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1.12 Open-Source Operating Systems
 Operating systems made available in source-code format rather than
just binary closed-source
 Counter to the copy protection and Digital Rights Management
(DRM) movement
 Started by Free Software Foundation (FSF), which has “copyleft” GN
U Public License (GPL)
 Examples include GNU/Linux and BSD UNIX (including core of Mac
OS X), and many more
 Can use VMM like VMware Player (Free on Windows), Virtualbox
(open source and free on many platforms - http://www.virtualbox.com)

Use to run guest operating systems for exploration
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End of Chapter 1
Operating System Concepts – 9th Edit9on
Silberschatz, Galvin and Gagne © 2013